48 PERSONAL APPEARANCES IN HEALTH AND DISEASE. 



for the supply of the pelvis and lower limbs. This great 

 arterial trunk, taking blood from the heart, is accompanied 

 in its course by a large venous trunk, the vena cava, 

 bringing back the blood from the lower extremities to the 

 heart. Much of. the blood from the viscera passes by 

 another route to the heart, viz., through the liver. 



Confined as it is within a rigid box, it is not likely that 

 the brain by any change in its shape can in the adult 

 exert any influence on the shape of the skull and there- 

 fore of the external configuration of the head. So it 

 happens that when any growth or tumour occurs in 

 connexion with the brain, it does not cause the skull to 

 change its shape, but rather the brain itself, which, being 

 of less resistance, yields, and is displaced by the new 

 growth. It is different, however, in infancy, when, as we 

 have seen, the bones of the skull are but imperfectly 

 developed, when their ossification is far from complete, 

 and when, soft in themselves, they are separated by still 

 softer and more yielding membrane. At this -period of 

 life if the brain enlarge it causes enlargement of the 

 skull, and the condition which best shows that is that 

 unfortunate condition popularly termed "water on the 

 brain," or technically " hydrocephalus." In this state 

 the brain is actually enlarged by the secretion of a large 

 excess of fluid in the spaces, or as they are termed 

 the ventricles, which exist within the nervous substance. 



